Our next guest, Bill Browder, knows quite a bit about the Russian lawyer who met with Donald Trump Jr. last year, a lawyer Trump says offered dirt on Hillary Clinton through an intermediary. Here's Browder's story. He was a hedge fund manager in Russia, where he made a lot of money but also learned a lot about corruption. In 2008, his lawyer, Sergei Magnitsky, uncovered a $230 million corruption scheme by a number of Russian officials. Magnitsky was arrested, jailed for almost a year and died in custody.

Browder says he was beaten to death. The Russian government says he died of a heart attack. Browder then pushed the U.S. Congress to pass something called the Magnitsky Act. It punishes Russian officials who were suspected of being involved in Magnitsky's death, denying their visas, freezing their assets. Russian President Vladimir Putin was so angry about this he ended his country's adoption program with the United States. So now back to this lawyer. She has worked hard to repeal the Magnitsky Act.

And Bill Browder is here to talk to us about that. Welcome to the show.

BILL BROWDER: Thank you.

MCEVERS: And when did you first meet this lawyer? Her name is Natalia Veselnitskaya.

BROWDER: I only met her once, and that was just a few months ago. But I've been on the other side of the barricades from her for the last three and a half years as she has been trying to get the Magnitsky Act overturned. And she's also the representative of a Russian government family who's had their assets frozen in New York by the Department of Justice when the Department of Justice traced those assets back to the crime that Sergei Magnitsky exposed.

MCEVERS: This $230 million dollar corruption scheme we mentioned. Yeah.

BROWDER: Exactly. And so I know her real well.

MCEVERS: Donald Trump Jr. released the emails this week that led to a meeting with Veselnitskaya. He was told by an intermediary she had damaging information about Hillary Clinton. She denies this, and she denies that she works for the Russian government. What do you say about that?

BROWDER: Well, I say it's complete nonsense. She is the representative of a family called the Katsyv family. The Katsyv family, the patriarch of that family is a man named Pyotr Katsyv. Pyotr Katsyv is a senior Russian government official who is closely aligned with Vladimir Putin. And so there's no way that she can - she can say that she has nothing to do with the Russian government when she works for a senior Russian government official.

MCEVERS: Right. But - so, you know, there's a way you can have some deniability, right? I'm not on the government payroll, but I represent somebody who's high up in the government. You know, there is a distinction there.

BROWDER: Well, in Russia, you know, nobody has a business card saying I work for the government. Russia's a very informal place where it's based on relationships and trusted agreements between people. And so...

MCEVERS: Right.

BROWDER: ...There's absolutely no question that she's working for the Russian government and that her objectives are to further the interests of the Russian government.

MCEVERS: And given what you know about the way the Russian government works, the way Russian President Vladimir Putin operates, what do you make of this meeting between her and Donald Trump Jr. and other members of the Trump campaign?

BROWDER: Well - so we have to go back to the Magnitsky case for a second. Vladimir Putin is infuriated by the Magnitsky case. Why is he infuriated by it? It's because he steals a lot of money himself. He ends up terrorizing people himself. And he keeps that money he's stolen offshore. And the Magnitsky Act basically imposes sanctions on people who do those types of things. And so this puts Putin's personal money at risk. So he made the repeal of the Magnitsky Act his single most important foreign policy priority. And if you speak to any Russians in the opposition who are against Putin they'll tell you that the Magnitsky Act is the thing that most upsets him, most infuriates him and he wants changed.

And so what has happened is that this woman, Natalia Veselnitskaya, via various people in the Russian government has become the proxy for Putin's interests in repealing the Magnitsky Act. And she has hired huge numbers of lobbyists and spent millions of dollars on lawyers, on public relations professionals, on smear campaigners with the objective of repealing the Magnitsky Act.

And obviously when Donald Trump was starting to rise and when he started to rise post-Republican nomination, I'm sure that they had a strategy meeting at headquarters and they said, we need to get to this guy to repeal the Magnitsky Act because this is their single most important foreign policy priority. And so they probably had embarked using all of their paid advisers to figure out how to get to Trump. And they finally found this odd in through this music promoter. And they went there with the sole objective of getting the Magnitsky Act repealed.

MCEVERS: Right. And what you speculate is some sort of quid pro quo. We'll give you information on your opponent if you'll consider doing away with this - the Magnitsky Act.

BROWDER: Well, what you have to understand is the Russians are extremely good at wheeling and dealing and pressuring and blackmailing and bribing and et cetera. I would have never gone to a meeting with something that they're asking for, something serious that they're asking for like repealing a major piece of human rights legislation, unless they could offer something equally tantalizing in return. Now, what they were offering we may never know. We don't know what really happened in that meeting. But surely they would have gone there with a very serious offer in exchange for what they were asking for.

MCEVERS: And how do we know that she - how do we know from her record, from her work that she is working against the Magnitsky Act?

BROWDER: Well, all you have to do is read her Twitter feed, read her Facebook page or read any of the articles about her. She funded a major film to Washington which was an anti-Magnitsky film. She hired various PR advisers. But most importantly she set up an NGO in Delaware whose sole purpose was to repeal the Magnitsky Act.

MCEVERS: Is it dangerous for you to talk about these things? I mean, you've received death threats before, right?

BROWDER: Well, because I'm working on something that's most upsetting to Putin I've received a number of death threats. I continue to be threatened. Is it dangerous for me to talk about these things? At this point it's probably actually more dangerous to not talk about them. Now, the most important thing is that Putin was responsible - he and his regime were responsible for murdering my lawyer, Sergei Magnitsky, and then covering up the murder.

And it's my mission, my life mission to go after the people that killed him and make sure they face justice. And the Magnitsky Act is a very important part of that. I'm trying to get the Magnitsky Act rolled out in other countries. We've just succeeded in getting it implemented in the United Kingdom. And we have the little country of Estonia that's just passed the Magnitsky Act. And Canada is on the 99-yard line and we should have it done by the fall. And this is a really important part of my fight for justice and my fight for the legacy of Sergei Magnitsky.

MCEVERS: Why do you say it's more dangerous if you don't speak out?

BROWDER: Well, they tend to like to kill people in a plausibly deniable way. And if you're quiet and people don't know what you're up to and they kill you, then nobody knows that they did it for one reason or another. If I'm speaking out as I have been and as I will be doing, at least if something happens everyone will know why they did it. And they don't want to get caught doing it, so perhaps that gives me a small bit of protection.

MCEVERS: Bill Browder, author of the book "Red Notice" with us on Skype. Thank you very much.

BROWDER: Thank you.

MCEVERS: And we should say NPR has made several attempts to reach Russian lawyer Natalia Veselnitskaya and she has not responded.